Copolymeric siloxanes



IN V EN TORS' ATTORNEY ARTHUR J. BARR) JOHN [if fi/LKEY In l 6'0 1'0 8'0 so DEGREES F.

CzHS Si 0 CH3 CH3 SiO CH3 A. J. BARRY EI'AL COPOLYMERIC SILOXANES Original Filed July 31, 1948 (CH3); SiO

TEMPERATURE AU 5 c m 5 2 0 May 27, 1952 Reissued May 27, 1952 COPOLYMERIC SILOXANES Arthur J. Barry and John W. Gilkey, Midland, Mich., assignors to Dow Corning Corporation, Midland, Mich, a corporation of Michigan Original No. 2,495,362, dated January 24, 1950, Serial No. 41,823, July 31, 1948. Application for reissue December 29, 1951, Serial No. 264,108

5 Claims. (Cl. 260-4482) Matter enclosed in heavy brackets I: appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

This invention relates to new compositions of matter comprising linear copolymeric siloxanes oi the type RzSiOECzHsCI-IaSiOhSlRa.

Copolymeric siloxanes oi the type (CH3) aSiOi (CH3) rSiOlnSKCHJ) s are known to the art. These materials are stable fluids possessing good temperature-viscosity behavior which renders them eminently adaptable for use as lubricants and damping media. However, the dimethylsiloxane trimethylsiloxane copolymeric fluids have freezing points in the neighborhood of -75 C. This limitation renders particularly the high polymers,-unsuitable for use in the extreme temperatures encountered at high altitudes and in the Arctic.

It is an object of this invention to provide materials which possess good stability and temperature-viscosity behavior and at the same time, have freezing points below -120 C. Another ob- Ject of this invention is to provide lubricants and damping media suitable for use on aircraft under any conditions encountered in nature. Other objects and advantages will be apparent from the following description.

This invention relates to copolymeric siloxanes oi the type (cm) iaslowimcmsim nsimcr'n') 2 where n has a positive value and R is a methyl or ethyl radical. These compounds may be in the form of distillable low molecular weight products in which n is an integer from 1 to 4 inclusive, or in the tom of non-distillable polymeric mixtures in which n has an average value greater than four.

These copolymers may be prepared from hydrolyzable silanes of the type (CI-1:):S1X, C2Hs(CH:|)2SiX and CHaCzHsSiX: where X is a halogen or alkoxy. Such silanes may be produced by any appropriate method. For example, they may be synthesized by the well known Grlgnard reaction. Alternatively, the ethylmethylsilanes may be prepared by reacting CHsHSlClz with ethylene under pressure to give CH3C2H5S1C12. This method is more fully disclosed in the copending application of Arthur J. Barry et al.. Serial Number 674,926, filed June 6, 1946, assigned to the Dow Chemical Company.

The hydrolysis of the silanes to give the copolymers of this invention may be carried out in two ways. The triorgano silane and the ethylmethylsilane may be mixed and cohydrolyzed and cocondensed by any 01' the methods known to the art. In such a process the reaction may be carried out either with or without a catalyst and in' the presence or absence of a solvent. It is preferred that the hydrolysis and condensation be carried out at temperatures between 0 C. and 250 C. The triorganosilane and the ethylmethylsilane may be hydrolyzed separately and the hexaorganosiloxane and the ethylmethylsiloxane-so obtained, which may be completely condensed, may be mixed and copolymerized by contacting them with an interaction catalyst such as a strong acid or an alkali metal hydroxide. In this method it is preferred that the temperature employed be between 80 and 200 C. A solvent may be used if desired.

The copolymers of this invention are linear in structure, and the molecules are composed of ethylmethylsiloxane chains end-blocked with trimethyl or ethyldimethyl silyl units. The lower members of both the homologous series may be separated from the reaction mixture by distillation.

The viscosity of the products obtained by cocondensing or interacting the triorganosilanes and the ethylmethylsilanes is readily controlled by regulating the molar ratio of triorgano to diorgano constituents. When the molar ratio of triorgano to diorgano silanes is high the viscosity of the copolymer product will be low. When this molar ratio is low the viscosity oi the product will be high. Thus, it is possible to obtain copolymers 01' any desired viscosity.

The trimethylsiloxane ethylmethylsiloxane and ethyldimethylsiloxane-ethylmethylsiloxane copolymers of this invention possess a combination of low freezing points and relatively small change in viscosity with temperature which renders them highly useful as low temperature lubricants and damping media. This combination of properties is both advantageous and unexpected.

'dimethylsiloxane copolymers, recourse may be had to the accompanying drawing. The drawing is a graph of the kinematic viscosity in cen methyl end-blocked ethylmethylsiloxanes are shown by lines AB, CD, and U, while the viscosity-temperature slopes ot'correspondins trimethyl end-blocked dimethylsiloxanes are shown by lines EF, GH and KL. It can be seen that the slopes of the copolymers this invention are equal to or superior to those 01' the dimethylcopolymers. A comparison of the freezing points of the present copolymers with trimethylsiloxanedimethylsiloxane copolymers is shown in Table I.

From the data given in this table it is readily seen that the copolymers of this invention extend the useful range of lubricants and damping media by more than 40 0., without loss of desirable temperature-viscosity properties.

For a better understanding oi this invention, the following examples, which should be considered as illustrative only. are given.

EXAMPLES Exusrts 1- below 20 C. by external cooling. This mixture was refluxed for 2 hours at 110 C. whereupon an acid layer and a product layer were formed. The acid layer was removed and the product layer was diluted with an equal volume of 5% NaOH. This mixture was heated for 2 hours at 88 C., with agitation, alter which the heat was removed and agitation was continued for an additional two hours. Residual NaOH was then removed. The fluid product was washed with H2O untfl neutral, dried, and filtered. The filtered product was then iractionally distilled and the following compounds were obtained in the percentages indicated:

(CH:)aSiOCaI-IaCI-IzSiOSUCHzh. 48.7% (CHflaSiOiCzHsCHzSiOlzSi(CHah. 26.5%

(CHahSiOwfl-IsCIhSiOhSNCE-na, 11.0%

and a residue of (CHahSlOWzI-IsCIhSiOhSHCHs)a, 15.8%

I Exmras 2 i This example illustrates the preparation oi trimethyl end-blocked linear ethyl methyl siloxanes from mixed ethylmethyl cyclic siloxanes and (CHzhSiOSHCl-Iah. 618 g. of mixed cyclic ethyl methyl siloxanes having the formula [Cal-IsCHaSiO]: were combined with 1378 g. of

(cmnslosucmn and 200 g. oi concentrated H'aSOs were added slowly to the 'mixturewith stirring. During the addition, the temperature did not rise above 30 C. After addition of the H2304, the mixture was agitated for two hours at room temperature. An acid layer and a product layer formed and were separated. The product layer was washed until neutral, dried over CaClz, and filtered. The fll tered liquid was then iractionally distilled and the following products were isolated in the proportions indicated:

(CHJhSlOCsHsCHJSiOSKCI-IJD, 43.5% (CH1)a8iO[CsHsCH:SiO]aS1(CH3):, 19.8% (CH:)JSiOlCsHsCHsSiOhSflCHsh, 7.7%

and

(CH3):SiO[C2HtCHJS10]:SI (CH1):

residue 29.0

Representative trlmethyi end-blocked ethylmethyl-slloxanes prepared and isolated as shown in Examples 1 and 2 are listed in the Table II.

Exmru: 3

Ethyldimethyl end-blocked ethylmethylsiloxanes were prepared according to the method shown in Example 1 by cohydrolyzing ethyldimethylohlorosilane and ethylmethyldichlorosilane. The properties of some 01' the copolymers of this series are given in Table III.

TABLE I Freezing Point, C.

Total Number Freezing Point, C.

Freezing Point, C.

76 below -12) below -1so ---84 below -uo below -120 below 12) below ii0 below -lfll below -11) TABLE 11 Beltactl Pom vs me Specific Compound Index Gravlt 31 Point, 5. at

0H: (CH;)s8i0[%i0 8i(Cfl|)| 173 1.3928 below -11) 830 CH (011;);8i0[%i0 Si(CHr); 227 1.4019 below -l20 .807

0H: (CHa)|8iO[BIO JSKCHQ: 263- 1.4060 below 120 can s OH: (CHs) 8iO[lJi%.]S1(CHs)s 311 1.4104 below --120 906 That which is claimed is: 1.

where R is selected from the group consisting of go where n is an integer from 1 to 4 inclusive.

25 where n has a positive value.

methyl and ethyl radicals and n has a positive 5. value.

where n has a positive value.

30 where n is an integer from 1 to 4 inclusive.

ARTHUR J. BARRY.

No references cited. 

